Systems for transferring graphene

ABSTRACT

The present disclosure is directed towards systems for transferring graphene from the surface of one substrate to another. In one particular embodiment, the graphene layer is grown on a surface of a first substrate, where the bottom of the first substrate is then affixed to the surface of a second substrate. The second substrate may include material made of a rigid or semi-rigid composition to provide structural support and backing to the first substrate. The graphene layer may then be delaminated from the first substrate and transferred to a target surface, such as the surface of an electronic device or biosensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/623,169 filed on Jun. 14, 2017, which claims the benefit of priorityto U.S. Provisional Patent Application Ser. No. 62/350,637 filed on Jun.15, 2016, the contents of which are incorporated herein by reference intheir entireties.

TECHNICAL FIELD

The disclosed technology relates generally to transferring graphene fromthe surface of one substrate to the surface of another. Morespecifically, embodiments disclosed herein relate to systems and methodsfor transferring graphene for large scale manufacturing.

BACKGROUND

Graphene is composed of a single thin layer of carbon atoms that arebonded together in a repeating pattern of hexagons. Graphene has manyextraordinary properties, which includes high mechanical strength, highelectron mobility, and superior thermal conductivity. Because grapheneis a great thermal and electrical conductor, graphene material is oftenused to construct graphene based biosensors, transistors, integratedcircuited, and other devices.

While there has been much academic interest in the application andutilization of graphene, attempts to commercialize graphene productionhave largely failed. As such, much of the currently known techniques forhandling and preparing graphene are limited to techniques that are onlysuitable for academic purposes and small-scale production, and thus failto take into consideration manufacturing costs, product assemblyrequirements, and the need for long-term durability. Additionally,because graphene layers are often grown on thin sheets, transferring thegraphene layer is often very difficult, especially since the thin sheetcan easily wrinkle and bend upon touch and even upon exposure to theenvironment.

While current methods of transferring graphene typically dissolve thesubstrate on which the graphene layer is attached onto, this is notideal because it dissolves the growth metal substrate and does not allowthe growth substrate to be reused. This not only substantially increasesmanufacturing costs, but is also likely to leave a thin residue on thegraphene layer since it is often difficult to completely dissolve themetal substrate. The remaining residue then leads to the contaminationand lowers the quality of the graphene.

Another method of transferring graphene may utilize adhesive tape todetach the graphene from the growth metal substrate and to transfer itonto the necessary surface. While the complexity and cost oftransferring graphene is low, this is not ideal for a commercial settingthat requires a large scale and high yield production of graphene. Assuch, there currently is a need for improving the transfer of graphenefor large scale manufacturing without damaging or contaminating thegraphene.

BRIEF SUMMARY OF EMBODIMENTS

In view of the above drawbacks, there exists a long felt need toproperly and effectively transfer a graphene layer from the surface ofone substrate to another, where the process is reliable and suitable forlarge scale production.

The present disclosure is directed towards the method of transferringgraphene from the surface of one substrate to another. In one particularembodiment, the graphene layer is grown on a surface of a firstsubstrate, where the bottom of the first substrate is then attached tothe surface of a second substrate. By way of example only, the secondsubstrate may include material made of a rigid or semi-rigid compositionso as to provide structural support and backing to the graphene layer.Some embodiments may further include delaminating the graphene layerfrom the first substrate and transferring the graphene layer to asurface of a third substrate, such as a surface of a sensor orelectronic device to complete the graphene transfer.

Other features and aspects of the disclosed technology will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, thefeatures in accordance with embodiments of the disclosed technology. Thesummary is not intended to limit the scope of any inventions describedherein, which are defined solely by the claims attached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The technology disclosed herein, in accordance with one or more variousembodiments, is described in detail with reference to the followingfigures. The drawings are provided for purposes of illustration only andmerely depict typical or example embodiments of the disclosedtechnology. These drawings are provided to facilitate the reader'sunderstanding of the disclosed technology and shall not be consideredlimiting of the breadth, scope, or applicability thereof. It should benoted that for clarity and ease of illustration these drawings are notnecessarily made to scale.

FIG. 1 is a flow chart illustrating a method for transferring graphenefrom a surface of a particular substrate to a surface of anothersubstrate according to one embodiment.

FIG. 2 is a diagram of a graphene layer on a surface of a particularsubstrate according to one embodiment.

FIG. 3 is a diagram of a graphene layer on a surface of a particularsubstrate with bubbling to transfer graphene onto a surface of anothersubstrate according to one embodiment.

FIG. 4 is a diagram of a transitory substrate of one embodiment.

FIG. 5 is a diagram of a transitory substrate with a growth substrateattached according to one embodiment.

FIG. 6 is a diagram of a system for delaminating a graphene layer from agrowth substrate according to one embodiment.

FIG. 7 is a diagram of a graphene layer delaminating from a substrateaccording to one embodiment.

The figures are not intended to be exhaustive or to limit the inventionto the precise form disclosed. It should be understood that theinvention can be practiced with modification and alteration, and thatthe disclosed technology be limited only by the claims and theequivalents thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following description is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles of thedisclosed embodiments. The present embodiments address the problemsdescribed in the background while also addressing other additionalproblems as will be seen from the following detailed description.Numerous specific details are set forth to provide a full understandingof various aspects of the subject disclosure. It will be apparent,however, to one ordinarily skilled in the art that various aspects ofthe subject disclosure may be practiced without some of these specificdetails. In other instances, well-known structures and techniques havenot been shown in detail to avoid unnecessarily obscuring the subjectdisclosure.

Some embodiments of the disclosure provide method of placing a graphenesheet or layer from one substrate to another substrate. FIG. 1 is a flowchart illustrating a method for transferring graphene from a surface ofone substrate to a surface of another substrate according to oneparticular embodiment. The method 100 may include growing a graphenelayer on a growth substrate at step 105. For example, the growthsubstrate may include a thin metal foil made of copper, nickel,ruthenium, gold and the like. However, it should be noted that thegrowth substrate is not limited to a thin metal foil, and may includeany growth substrate proper for growing a graphene layer. Additionally,the graphene layer grown on the growth substrate may be placed in afurnace or applied with high temperature to accelerate and ensure propergrowth of the graphene layer.

The method 100 may further include step 110, which includes attachingthe growth substrate with the grown graphene layer onto a the surface ofa transitory substrate. Because the growth substrate may be a thinlayer, such as a thin foil, the thin foil is likely to wrinkle and bendwhen being handled or exposed to certain environmental conditions. Ifthe thin foil is compromised, the graphene on the thin foil will then bedamaged and likely even contaminated. As such, by way of example only,attaching a transitory substrate to the thin foil may provide thenecessary support, rigidity, and backing to prevent the thin foil frombending, wrinkling, or disturbing the graphene layer. By way of exampleonly, the transitory substrate may include material made of glass,plastic, metal, silicon, silicon oxide, aluminum, aluminum oxide, andother insulators or metals

The growth substrate may be affixed to the transitory substrate with theuse of an adhesive. For example, an adhesive layer may be placed on thesurface of the transitory substrate, such that the thin foil is thenplaced directly on top of the adhesive to properly affix the thin foilto the rigid substrate. In another example, the adhesive layer may alsobe placed on the surface of the thin foil opposite from the side withthe graphene layer. The use and application of the adhesive layer mayhelp ensure that the thin foil is smooth and unwrinkled so that thegraphene layer is not damaged. Additionally, a nitrogen steam may begently applied so as to further press the thin foil into the adhesivelayer.

Next, the method 100 may further proceed to step 115, which may includedepositing the graphene layer with a protective coating or layer toprovide further structural support and a protective covering to thegraphene layer. It should be noted that depositing layers onto thegraphene sheet may include a wide range of techniques as appreciated byone of ordinary skill in the art, such as coating techniques, focusedion beam, filament evaporation, sputter deposition, and electrolysis byway of example only.

In some embodiments, the protective coating may be a polymer, such asPoly-methyl methacrylate (hereinafter “PMMA”), by way of example only.The PMMA coated graphene layer may then be cured under ambientconditions or via heat to sufficiently ensure that the PMMA adheres ontothe graphene layer. Once the PMMA properly adheres onto the graphenelayer, the graphene layer may be cut or stamped into the desired shapeand dimension using a sharp-edged tool. However, the protective coatingneed not be limited to a PPMA polymer, and instead, may include anycarbon backbone polymer to be used as a coating for the graphene layer.

Additionally, by applying a protective covering to the graphene layer,this allows the graphene to be handled by machinery and othermanufacturing conditions without having to worry about contaminating ordamaging the graphene layer.

The method 100 may further include step 120, which may includedelaminating the graphene layer from the growth substrate, thus allowingthe graphene layer to then be transferred to another surface, such asthe surface of an electronic device by way of example only. Todelaminate the graphene layer, the growth substrate may be connected tothe anode of an electrochemical cell, where the cathode is thensubmerged in a conductive ionic solution to complete the circuit. By wayof example only, the conductive ionic solution may include a sodiumhydroxide solution that ranges from 0.05 to 3 molar concentration.However, the ionic solution need not be limited to a sodium hydroxidesolution, and instead, may include other ionic solutions such aspotassium hydroxide, hydrogen chloride, and the like. Additionally, theelectrochemical cell may include a voltage source that is configured togenerate 20-50 V. By applying potential to the electrochemical cell,hydrogen and oxygen bubbles may evolve at the electrodes, such that thebubbles are situated in between the growth substrate and the graphenelayer. This may then cause the graphene layer with the protectivecoating to separate from the growth substrate, such that the graphenelayer with the protective coating then floats to the surface of theionic solution.

Next, the method 100 may proceed to step 125, which may includetransferring the graphene layer with the protective coating onto thesurface of a target substrate. For example, the surface of a targetsubstrate may be the surface of an electronic device or biosensor by wayof example only. However, it should be noted that the surface of atarget substrate may be any surface that may receive and harbor agraphene layer. However, before placing the coated graphene layer on thesurface of a target substrate, the graphene layer with the coatedprotective layer may first be washed in deionized water baths to removeany residual ions. The graphene layer with the coated protective layermay then be affixed to the surface of the target substrate via capillaryforces. To further ensure that the graphene layer is properly andsecurely adhered to the surface of the target substrate, the graphenelayer may be cured in ambient conditions from anywhere near 30 minutesto 24 hours to allow any remaining trapped water to dry out. Thisprocess of transferring graphene may be capable of transferring 99% ofthe graphene layer from the surface of the growth substrate to thesurface of a new target substrate.

The method 100 may then proceed to step 130, which may include removingthe protective coating on the graphene layer, such that only thepristine graphene layer is adhered to the surface of the targetsubstrate. For example, the protective coating may be removed byutilizing an acetone wash, which leaves only the graphene layer on thetarget substrate.

FIG. 2 is a diagram of a graphene layer 220 supported by a transitorysubstrate 205 for transferring the graphene layer 220 according to oneembodiment. As illustrated, the graphene layer 220 is grown on a growthsubstrate 215, which may include a thin metal foil made of copper ornickel by way of example only. The thin metal foil of the growthsubstrate 215 may also be affixed to the transitory substrate 205 so asto prevent the thin metal foil from bending or wrinkling when handlingor transferring the graphene layer 220. To further ensure that the thinmetal foil of the growth substrate 215 is properly flattened and affixedto the rigid substrate 205, an adhesive layer 210 may be applied so asto adhere the bottom of the growth substrate 215 onto the top surface ofthe rigid substrate 205.

Because the graphene layer 220 is exposed to the environmentalconditions and is highly susceptible to contamination and damage, thegraphene layer 220 may include a protective coating 225, such as PMMApolymer by way of example only. The coating may provide the necessarystructural support and proactive covering to protect the graphene layerthroughout the transfer process.

FIG. 3 is a diagram of a graphene layer 320 on a surface of a growthsubstrate 315 with bubbling 330 present in between the graphene layer320 and the growth substrate 315. Additionally, the graphene layer 320may further include a protective coating 325 so as to protect theexposed portion of the graphene layer 320. Similar to FIG. 2, the growthsubstrate 315 may be affixed to a transitory substrate 305 via anadhesive layer 310, so as to prevent the growth substrate from bendingor wrinkling when handling or transferring the graphene layer.

In order to transfer the graphene layer 320 onto a surface of anothersubstrate, the graphene layer must first be detached from the growthsubstrate 315. To do so, an electrode potential may be applied so thatthe anode of an electrochemical cell is connected to the thin metal foilof the growth substrate 315 and the cathode is submerged in a conductiveionic solution to complete the circuit. By applying the potential,hydrogen and oxygen bubbles 330 may form in between the thin metal foilof the growth substrate 315 and the graphene layer 320. With theformation of the hydrogen and oxygen bubbles 330, the graphene layer 320may be gently delaminate from the thin metal foil of the growthsubstrate 315. This allows the coated graphene layer 320 to detach fromthe growth substrate 320, thus allowing the graphene layer to then beplaced on a surface of a selected target substrate.

FIG. 4 is a diagram of a growth substrate 401 of one embodiment. Asillustrated, the growth substrate 401 may include material made ofcopper or any other material suitable for growing a graphene layer. Byway of example only, an embodiment may further include scoring thetransitory substrate with score marks 402 or windows on a surface of thegrowth substrate 401. The score marks 402 may be added at thesurrounding edges of the growth substrate 401. The score marks 402 maybe added to help guide the bubbles in between the graphene layer and thegrowth substrate 401 when the growth substrate 401 containing a graphenelayer is submerged into a conductive ionic solution. Without theplacement of the score marks 402, the bubbles are likely to aggregate atthe outer edges of the growth substrate 401, which is not ideal and notlikely to provide a clean delamination of the graphene layer from thegrowth substrate 401. Thus, by including the score marks 402 at thegrowth substrate 401, this allows the bubbles to more effectivelypenetrate and be situated in between the growth substrate 401 and thegraphene layer, thus ensuring a gentle and full delamination of thegraphene layer from the growth substrate 401.

By way of example only, the score marks 402 may be formed along theedges of the growth substrate 401, but not less than 1 mm from the edgeon all sides of the growth substrate. Additionally, in otherembodiments, the score marks 402 may be added along the areas where theedge of the graphene is to be situated on top of the growth substrate401.

By way of example only, the growth substrate 401 may have dimensionswhere the length 404 of the growth substrate 401 may range from 1 inchto 12 inches. Additionally, in another example, the growth substrate 401may have a width 405 that ranges from 1 inch to 6 inches. However, itshould be noted that these exemplary dimensions are in no way limitingand may include any length 404 and width 405 as smaller and/or greaterthan one inch as appreciated by any one of ordinary skill in the art.

FIG. 5 is a diagram of a transitory substrate 501 with a growthsubstrate 503 deposited on top according to one embodiment. Here, thegrowth substrate 503 may be a thin metal foil that may easily be bent orwrinkled, which then will damage the graphene layer grown on top of thegrowth substrate 503. As a result, the growth substrate 503 may betransferred onto a transitory substrate 501, where the transitorysubstrate 501 provides a supportive platform to protect the integrity ofthe growth substrate 503. Additionally, by way of example only, thetransitory substrate 501 may have dimensions that ranges in 0.5 inchesto 1 inch longer and wider than the dimensions of the growth substrate503. This then allows for a personnel or machine to handle thetransitory substrate 501 without having to touch or make contact withthe graphene layer, thus further preventing the likelihood ofcontamination and damage to the graphene layer.

Furthermore, the transitory substrate 501 may include an adhesive layer505 on top, where the adhesive layer 505 is strategically placed inbetween the top surface of the transitory substrate 501 and the bottomsurface of the growth substrate 503. Again, the adhesive layer 505 mayhelp ensure that the growth substrate 503 is smooth and unwrinkled sothat the graphene layer growing on top is not damaged.

As discussed with respect to FIG. 4, the growth substrate 503 mayinclude score marks 504 along the areas where the edge of the grapheneis to be situated on top of the growth substrate 503.

FIG. 6 is a diagram of a system 600 for delaminating a graphene layeraccording to one embodiment. Here, the system 600 may include acontainer 604 for holding conductive liquid used to delaminate thegraphene layer from a substrate 602, such as a growth substrate. Assuch, the substrate 602 may be immersed into the conducive liquid tobegin the delamination by placing the substrate onto a platform 607attached onto an arm 606 with an actuator and platform 607.

The linear actuator may allow for the platform 607 to proceed up anddown the arm 606 at a controlled rate, thus allowing to control thesubmersion rate of the substrate 602 into the conductive liquid. By wayof example only, the arm 606 may be configured so that the platform 607has a steady immersion rate, where the platform with the graphene layermay enter and exit the solution at a steady rate ranging from 0.5 mm/sto 10 mm/s. By way of example only, the average entry and exit rate maybe 2 mm/s. Additionally, by way of further example only, the immersionrate may correspond to a delamination rate, where the graphene is thenproperly and cleanly delaminated from the transitory substrate.

Additionally, the entry and exit rate of the platform containing thesubstrate with the graphene layer may require close observation todetermine if the graphene is properly and cleanly delaminating from thesubstrate 602. For example, if the entry of the substrate 602 isproceeding too quickly into the conductive liquid, the graphene layermay not properly delaminate from the substrate. The proper delaminationof the graphene from a substrate is depicted in FIG. 7. As illustrated,graphene layer 701 is gently being separated from the growth substrate702 when immersed in the container 703 filled with conductive solution.

However it should be noted that the platform need not be connected to anactuator to immerse the platform in and out of the conductive solutionat a steady immersion rate. Instead, the platform may simply be placedin the conductive solution for a select period of time to delaminate thegraphene from the transitory substrate. When the delamination iscomplete, the platform containing the graphene sheet and the transitorysubstrate was simply be taken out of the conductive solution.

As such, referring back to FIG. 6, some embodiments of the system mayinclude a camera 601 directly on top of the container 604 to monitor thedelamination of the graphene layer. Thus, a viewer may be able tomonitor the delamination process via the camera feed provided by thecamera 601. Furthermore, in other embodiments, the linear actuator maybe connected to the camera 601, where the linear actuator is placed infeedback loop for automation.

The container 604 may also be placed on a colored background 605 forcontrast. By providing a colored background 605, this may allow a viewerto quickly view and see the delamination of the graphene layer withease. Additionally, to further distinguish the layers on the substrate,the temporary protective coating on top of the graphene may also becolored, which further allows the viewer to view the progress of thegraphene layer being delaminated.

Additionally, this transfer process is not limited to the transfer ofgraphene. Indeed, this transfer process may also be applied to other lowdimensional materials, that include, but are not limited to, carbonnanotubes, molybdenum disulfide, phosphorene, tungsten diselenide, andthe like.

While various embodiments of the disclosed technology have beendescribed above, it should be understood that they have been presentedby way of example only, and not of limitation. Likewise, the variousdiagrams may depict an example architectural or other configuration forthe disclosed technology, which is done to aid in understanding thefeatures and functionality that can be included in the disclosedtechnology. The disclosed technology is not restricted to theillustrated example architectures or configurations, but the desiredfeatures can be implemented using a variety of alternative architecturesand configurations. Indeed, it will be apparent to one of skill in theart how alternative functional, logical or physical partitioning andconfigurations can be implemented to implement the desired features ofthe technology disclosed herein. Also, a multitude of differentconstituent module names other than those depicted herein can be appliedto the various partitions. Additionally, with regard to flow diagrams,operational descriptions and method claims, the order in which the stepsare presented herein shall not mandate that various embodiments beimplemented to perform the recited functionality in the same orderunless the context dictates otherwise.

Although the disclosed technology is described above in terms of variousexemplary embodiments and implementations, it should be understood thatthe various features, aspects and functionality described in one or moreof the individual embodiments are not limited in their applicability tothe particular embodiment with which they are described, but instead canbe applied, alone or in various combinations, to one or more of theother embodiments of the disclosed technology, whether or not suchembodiments are described and whether or not such features are presentedas being a part of a described embodiment. Thus, the breadth and scopeof the technology disclosed herein should not be limited by any of theabove-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives can be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

1. A system for transferring graphene comprising: a graphene wafercomprising: a growth substrate for growing a graphene layer; and atransitory substrate affixed to the growth substrate; a container filledwith conductive solution; and an arm connected to a platform to immersethe platform in and out of the conductive solution.
 2. The system ofclaim 1, wherein the arm is connected to a linear actuator for immersingthe platform in and out of the conductive solution at a steady immersionrate.
 3. The system of claim 1, further comprising a camera to provide acamera feed of the container for monitoring a delamination of thegraphene layer from the growth substrate.
 4. The system of claim 1,wherein the growth substrate comprises copper.
 5. The system of claim 1,wherein the transitory substrate comprises glass, plastic, silicon, orsilicon oxide.
 6. The system of claim 5, wherein the transitorysubstrate comprises an adhesive layer on the transitory substrate toaffix the growth substrate to the transitory substrate.
 7. The system ofclaim 1, wherein the transitory substrate comprises metal, aluminum, oraluminum oxide.
 8. The system of claim 7, wherein the transitorysubstrate comprises an adhesive layer on the transitory substrate toaffix the growth substrate to the transitory substrate.
 9. The system ofclaim 1, wherein the transitory substrate comprises score marks on asurface.
 10. The system of claim 9, where each score mark is locatednear an edge of the transitory substrate.
 11. The system of claim 10,wherein the score marks provide a space for bubbles to be situated. 12.The system of claim 11, wherein the bubbles cause the graphene todelaminate from the transitory substrate at a delamination ratecorresponding to a steady immersion rate of the platform.